Designing ferrierite-based catalysts with improved properties for skeletal isomerization of n-butene to isobutene

Abstract

The crystal morphology and size of ferrierite catalysts were controlled by a suite of crystallization methods and structure-directing agents. In particular, nano-sized ferrierite could be obtained by using tetramethylammonium hydroxide and pyrrolidine as double structure-directing agents under dynamic crystallization. The catalysts were analysed by XRD, SEM, N 2 adsorption-desorption, NMR, XRF, NH 3 -TPD, Py-IR, and TGA, and the characteristics were correlated with their catalytic performance in the skeletal isomerization of n-butene. The results clearly indicated that all the catalysts have a similar crystallinity, Si/Al ratio, and total number of acid sites, while a decrease in their crystal size leads to more pore mouth acid sites. The nano-sized ferrierite showed better stability and higher activity, which were related to their crystal morphology, size, and pore mouth acid. In addition, we further confirmed that high isobutene selectivity can be produced by monomolecular reaction.

Synthesis of Nano‐Hierarchical Ferrierite with Sole Template and Its Catalytic Application in n‐Butene Skeletal Isomerization

“…Here, the catalytic performance in n ‐butene skeletal isomerization of nano‐hierarchical FER (S2) and commercial FER (NKU catalysts,SC)were investigated.It can be seen form Figure ,S2 and SC presented similar initial conversion of n ‐butene,however the stable n ‐butene conversion of S2 was much higher than commercialize FER .According to Figure –,the isobutene selectivity of S2 and SC were increased with the extension of reaction time,but the selectivity of main byproducts(protene+pentene) showed opposite trend, which were agreement with previous results about FER , moreover,the stable isobutene selectivity of S2 and SC were more than 90%.Therefore,the isobutebe yield of S2 was much higher than that SC as shown in Figure…”

“…Hierarchical zeolite can effectively solve diffusion restrictions because of its larger external area and more mesoporous (2∼50 nm) and macroporous (>50 nm) channels, moreover,the shape selecting catalysis of hierarchical zeolite is almost not effect attribute to retaining microstructure. At present, there are two main ways to prepare hierarchical zeolite : one is post‐treatment, mesoporous structures are made by acidic or alkaline modification, which is sample and effective,but leads to partial destruction of zeolite framework structure, in addition, dealuminization by acid treatment easily leads to the formation of non‐framework aluminum and then changes the acidity distribution of zeolite; the other one is direct synthesis,intercrystalline mesoporous is formed by reducing crystal size,which not only introduces a large number of ordered mesoporous pores, but also hardly change the acidic distribution of zeolite, however most direct synthesis methods of hierarchical zeolite require the addition of second Organic structural direct agent( OSDA ),which not only increases the cost of synthesis but also causes pollution easily …”

“…Ferrierite (FER ) contain a two‐dimensional channel system composed of a 10‐member ring ( 10‐MR ) channel (0.42×0.54 nm) parallel to the crystallographic direction of [001] and an 8‐member ring ( 8‐MR ) channel (0.35×0.48 nm) parallel to the direction of [010].According to reports, FER shows good catalytic performance in the reactions of n ‐butene to isobutene, olefin made from methanol, and catalytic reduction of NOx . Hierarchical FER synthesized by direct synthesis method forms mesoporous channels by intercrystalline accumulation of nanocrystalline grains, which showed better catalytic performance,especially for the reaction of n ‐butene skeletal isomerization . Up to now, many methods have been reported to prepare nano‐hierarchical FER .…”

“…Christian synthesized nanosized, needlelike FER with choline and Na + cations as OSDAs after crystallization under rotation at 150°Cfor 14 days . Wang synthesized column‐like aggregates consisted of tightly packed primary nanocrystal grains with piperidine and tetramethylammonium hydroxide as OSDAs , and Hu synthesized flake packed hierarchical FER under rotation with same OSDAs . However, most synthesis methods of nano‐hierarchical FER at present are needed second template or dynamic crystallization, which not only increases synthesis costs greatly, but the high demands are proposed for equipment under dynamic state.…”

Acetonitrile Synthesis via Ammoxidation: Mo/zeolites Catalysts Screening

“…Ferrierite is a medium-pore sized zeolite containing a bi-dimensional pore system consisting of 10 membered ring (MR) channels (4.3×5.5 Å) and 8 MR channels (3.5×4.8 Å) [27,28] . The interaction between molecules having permanent moment (e.g.…”